Contents

Tecumseh 5 HP Engine

Executive Summary

This wiki documents the the three phases of the analysis of a 5 Horsepower Tecumseh engine. This engine was originally used to power a push lawnmower, but the analysis below begins after it had been removed from the mower body, and covers only components of the engine.

The first phase of this project focused on the disassembly and analysis of the motor's condition. It was determined that this motor probably did not run due to a faulty piston ring.
During the second phase group members cataloged and analyzed each of the approximately 38 total parts.

The final phase of the project involved reassembling the motor, and reflecting on its overall design. Based on the understanding of the engine during the previous phases recommendations are made regarding the design, manufacturing, use, and life-cycle of the engine.

Introduction

This product was used to run a push mower. It is powered by an internal combustion that is used to spin the blades. Based on the condition of its parts this engine will not run, but this has not been tested.

Group Members:

Ian Kelsey - disassembly, reassembly, wiki creation

Dan Leake - disassembly, wiki creation

Kyle Johnson - disassembly, reassembly

Alex Lovallo - disassembly, reassembly, wiki creation, team leader

Sanket Chavan -

Product Description

5 Horsepower Lawnmower Engine

Manufacturer: Tecumseh

Model Number:

Before Dissasembly

This 5 HP engine was used to power a pull start lawnmower. It was likely intended for urban or small yard use as it does not seem to have a drive system for its own locomotion. This engine once transformed chemical energy from combustion into linear kinetic energy using its piston. The connecting arm and crankshaft then converted this linear reciprocation motion into translational motion which could be used to power the mower blades directly, or may have been fed to the blades by a belt system.

It is possible that this engine will run as it does seem to have compression when the pull cord is pulled. While it is not possible for us to test this mower these is strong evidence that it will not run, or at least will only run for a short while until it breaks. The muffler of the engine is full of oil that will run out if it is tipped. This indicates that the piston rings may have failed and the engine is burning oil. Failed piston rings result in a lot of sediment build up from the burnt oil as well as increased piston friction which can significantly reduce the life of the engine. If enough heat builds up parts of the engine can melt rendering it inoperable.

Not including any fasteners it seems like that this engine will have roughly 40 parts. Viewing the exterior of the motor it is clear that plastic, and steel or iron have been used. Inside we expect to come across more iron, steel, rubber, and potentially some sort of textile.

After Disassembly

Disassembly Process

Step Number

Process

Tool

Level of Difficulty

1

Remove 7 Phillips-head screws

Phillips-head Screwdriver

Easy, 1 Screw Quite Difficult

2

Removed Rip Fence Bolt to Saw Blade Locking Lever

By Hand

Easy

3

Removed Removed Dust Blower Angle off of Dust Blower

By Hand

Easy

4

Removed Dust Blower and Rip Fence off of Casing

By Hand

Easy

5

Removed Rip Fence off of Casing

By Hand

Easy

6

Removed Plastic Blade Guard off of Casing

By Hand

Easy

7

Removed Casing off of Casing

Philips-head Screwdriver

Moderately Easy

8

Removed Gel Max Comfort Grip off of Casing

By Hand

Easy

9

Removed Shoe Plate Locking Gear off of Casing

By Hand

Easy

10

Removed Shoe Plate Locking Knob off of Casing

By Hand

Easy

11

Removed Trigger Switch off of Casing

By Hand

Easy

12

Removed Lock on Button off of Trigger Switch

By Hand

Easy

13

Removed Lock Spring off of Lock on Button

Flat-head Screwdriver

Easy

14

Removed Plastic Lock Washers off of Lock on Button

Flat Head Screwdriver

Moderately Difficult

15

Removed Switch Breaker off of Trigger Switch

By Hand

Easy

16

Removed 2 Cord Clamp Screws off of Cord Clamp off of Casing

Phillips-head Screwdriver

Easy

17

Removed Red Motor Connecting Wire off of Spring Loaded Graphite

By Hand

Easy

18

Removed Black Motor Connecting Wire from Spring Loaded Graphite

By Hand

Easy

19

Disassembled Spring Loaded Graphite Internals

By Hand

Easy

20

Removed Motor Screw From Casing

Philips-head Screwdriver

Easy

21

Removed Red Motor Connecting Wire From Armature

By Hand

Easy

22

Removed Black Motor Connecting Wire from Armature

By Hand

Easy

23

Removed Metal Gear From 1/4in. Plate

By Hand

Easy

24

Removed 1/4in. Metal Plate from Armature Shaft With Rotar

By Hand

Easy

25

Removed Small Metal Plate off of Armature Shaft With Rotar

By Hand

Easy

26

Removed Linear Oscillator from Metal Gear

By Hand

Easy

27

Removed Washer off of Gear from Metal Gear

By Hand

Easy

28

Removed Cylindrical Slider from Linear Oscillator

By Hand

Easy

29

Removed Blade Changing Piece from Blade Changing Component

By Hand

Difficult

30

Removed Blade Changing Spring from Blade Changing Component

By Hand

Easy

31

Removed Allen Wrench Screw from Blade Changing Component

3/32 Allen Wrench

Easy

32

Removed Blade Changing Component from Linear Oscillator

By Hand

Easy

33

Removed Felt Piece from Linear Oscillator

By Hand

Easy

34

Removed Cylindrical Slider 2 from Linear Oscillator

By Hand

Easy

Component List

Part #

Component Name

Quanity

Material(s)

Manufacturing Process

Description of Function

Image

Physical Description

1

Gas Cap

1

Plastic

Injection Molded

To seal the gas tank, by means of interior threading and a rubber gasket, to prevent leakage but yet allow air to pass into the tank to allow the free flow of gas out of tank

U-shaped bracket surrounding a black cube. Both have layered steel in the ends. Spark plug wire comes from rear. Small strip for attaching grounding wire. Has plastic spray coating to seal the back side

19

Nut, washer and pull string catch

1

Steel

Stamped and machined steel.washers are stamped from sheet metal, nuts are extruded then cut and bored out

Teeth on interior cause rotation of crank when pull string is pulled to start motor.

cup shaped steel piece. With teeth on inside. Hole in top center for affixing bolt

Throttle connected to butterfly valve to control gas input to combustion chamber. Throttle cable holds throttle open while in operation. When the cable is not under tension the throttle closes because of attached spring breaking the electrical connection to pick up coil. Preventing spark stopping engine

Flat plate with hinge and spring to throttle control and grounding wire

22

Carburetor

1

Cast iron, steel , rubber

Portion is die cast iron, stamped steel, extruded rubber

Carburetor controls mixture of gasoline and air flowing to the combustion chamber. Cylidrical shape filters the gasoline before combustion

Cylindrical with rubber primer on side. One input for gas, two holes for air flow. Throttle butterfly valve on interior. Wire arm attached to throttle

One valve controls air/fuel intake into combustion chamber. Second valve controls exhaust out of chambers

Long cylinder and thing with flattened head. Filleted near head

25a

Valve spring

2

Steel

Coiled, hot wound, and hardened in form

Holds valves shut until proper time

Spring

25b

Valve spring clip

2

Steel

Punched

Secures spring to valve

Two diameters of ring on top of each other. Smaller diameter can fit inside of spring. Has slot in middle for valve stem to slip into

26

drive pulley

1

Steel

Machined

Connects to crank shaft to use engine power to drive belt

Hollow cylinder with groove around outside edge and key way through inside

27

10 mm bolts with washers

6

Steel

Extruded steel rods that are thread rolled

Attached crank case to the motor block

Bolts

28

Key from crank shaft

1

Steel

Stamped

Hold drive pulley in line with crank shaft so they rotate together

Small half cylinder cut along long axis

28a

Crank case pins

2

Steel

Cut steel bar

Align crank case bolts holes with the blocks bolt holes

Short cylinders with rounded ends

29

Crank case cover

1

Cast iron

Die cast iron then machined

Holds parts and oil inside crank case.

Rounded shape with holes to affix to crank case, holes for aligning pins, holes in center for crank shaft. Interior cavity to hold and align camshaft and camshaft aligner

30

Cam shaft

1

Cast iron

Die-cast then machined

Powered by crank shaft, has gear and lobes sized to open and close valves at proper time

Shaft with two lobes, a central gear, smooth and cylindrical on both ends

31

Valve lifters

2

Steel

Welded and Machined Steel

Are pushed up by lobes of cam shaft. When pushed up they open the valves in the combustion chamber

Flat plate with cylindrical shaft attached

32

Connecting rod cap

1

Cast aluminum

Cast and then machined

Holds the connecting rod to the crank shaft

Semi-circular curved bar with a bolt hole on either end. Inner surface is machined . Inside of surface is machined to reduce friction

32a

1/4" hex-head bolts

2

Steel

Extruded steel rods that are thread rolled

Fasten connecting rod cap to connecting rod over crankshaft

Bolts

33

Crank shaft

1

Cast iron with machined parts

Cast and then machined to specifications

Translates reciprocating linear piston motion into rotation

Cylindrical shaft with an offset cylinder in the middle, has two counter weights near middle

33a

Washer

1

Steel

Punched

To reduce friction on the crankshaft

Flat round ring made of steel

34

Connecting rod

1

Cast aluminum

Cast the machined

Connects the piston to the crankshaft transmitting the power

I shaped bar with circular hole on one end and semicircular groove on the other end that mirror the shaped of the connecting rod cap. Has a bolt hole on either side of the semi circular end to interface with the connecting rod

35

Wrist or gudgeon pin with a clip

1

Steel

Pin is machined from solid stock, Clip is shaped and heated to hold form.

Connects the piston to the connecting rod and provides a bearing for the connecting rod to pivot as it moves

Tube is a bored out cylinder and clip is shaped like a lowercase e

36

Piston

1

Aluminum Alloy

Cast and machined to specifications.

Transfers the force from combustion gas in the cylinder to the crankshaft via the connecting rod. Forces exhaust out of exhaust valve and draws the air fuel mixture into the combustion chamber. Compresses the air/fuel mixture pre-combustion

Cylindrical with flat plane on one end. Has lateral hole to allow wrist pin. Has grooves in side for piston rings and a hollowed interior to reduce mass

36a

Piston Rings

3

steel and coated steel

Punched steel, One ring has a spring coating along outside edge

Seal the combustion chamber/ Support heat transfer from the piston to the cylinder wall/ Regulate engine oil consumption

Each ring has one gap. One ring is not solid steel but has a composite material insert

37

Engine block

1

Cast iron

Die cast and machined to specifications

Houses all of internal engine parts

Hollowed rectangle with fins

38

Cam shaft aligner

1

Plastic ring with stainless steel rod in it

Machined steel, injection molded plastic

Holds one end of the cam in place to insure that the teeth between the crankshaft gear and camshaft gear align

Plastic ring with extruded tube off one side with a steel insert in it